Although HIV peptide presentation is the first step leading to immune recognition we still do not know which peptides are presented by productively infected cells such as CD4 T cells and macrophages, and which peptides are presented by dendritic cells (DC) during vaccination. Solving this challenge is of high significance for the vaccine field even beyond HIV. Successful immunogen design strategies should aim at 1) recognizing infected cells before HIV transfer to neighboring cells, 2) recognizing all infected cell subsets regardless of the path of viral entry into cells, 3) encompassing HIV protein fragments allowing epitope presentation by DC and matching the landscape of epitopes displayed by HIV-infected cells. We performed the first isolation of intracellular epitope precursors and MHC-bound HIV-derived peptides and revealed a greater than expected diversity of nested peptides presented by HIV-infected cells. We identified differences in antigen processing activities among HIV-infectable cell subsets and between cytosol and endolysosomes (compartments in which the virus traffics), suggesting that HIV peptides available for MHC loading may vary with regards to length, kinetics of presentation and amount of peptides displayed by cells. Finally we identified FDA-approved drugs modulating peptidase activities, protein degradation and peptide presentation in a predictable manner. We propose to develop and test in vitro and in humanized mice a new concept of vectorless immunogen co-delivered with drugs that will modulate epitope presentation by DC during vaccination to match presentation by infected cells. Using our assays to follow HIV protein degradation into MHC-I and MHC-II epitopes, to identify MHC-bound peptides, to manipulate protein degradation with drugs, and to perform real-time epitope presentation to T cells we propose to 1) Identify HIV-derived fragments leading to epitope presentation by all infected cells prior to virion release, 2) Transiently manipulate antigen processing in DC to match early epitope presentation by HIV-infected cells, 3) Link epitope processing and presentation by DC to priming of desired T cell responses. This proposal builds on a multidisciplinary collaboration linking the PI's expertise in antigen processing and presentation, and experts in computational analysis, T cell priming, nanoparticles and immunogen design and in vivo testing. We aim at developing an immunogen eliciting sustainable immune responses clearing infected cells -- regardless of the mode of virus entry -- before new HIV virions are transmitted to other cells, thus preventing the establishment or propagation of HIV infection.